As electrophotographic photosensitive members, in view of advantages, such as low cost and high productivity, electrophotographic photosensitive members (organic electrophotographic photosensitive members) having a photosensitive layer (an organic photosensitive layer) which uses an organic material as a photoconductive substance (a charge generating substance or a charge transport substance) and which is disposed on a cylindrical support have been widely used. Furthermore, as organic electrophotographic photosensitive members, in view of advantages, such as high sensitivity and a possibility of designing various materials, electrophotographic photosensitive members having a lamination-type photosensitive layer in which a charge generation layer containing a charge generating substance and a charge transport layer containing a charge transport substance are stacked have been mainly used.
Since electrical/mechanical external forces due to charging, exposure, development, transfer, cleaning, and the like are applied to the peripheral surface of an electrophotographic photosensitive member, many problems are caused by these forces. Specific examples of the problems include degradation in durability due to flaws and abrasion on the peripheral surface of the electrophotographic photosensitive member, degradation in transfer efficiency, melt adhesion of toner, and image defects due to inadequate cleaning.
In dealing with the problems, it is known to be effective to roughen the peripheral surface of the electrophotographic photosensitive member for the purpose of imparting releasability and lubricity. Specifically, by roughening of the peripheral surface of the electrophotographic photosensitive member, when a toner, a charging member, a transferring member, a cleaning member, or the like is brought into contact with the peripheral surface of the electrophotographic photosensitive member, the contact area can be reduced. Consequently, effects of improving releasability and reducing frictional force are expected. The frictional force between the peripheral surface of the electrophotographic photosensitive member and the cleaning blade is particularly large, resulting in degradation in cleaning performance and degradation in durability of the electrophotographic photosensitive member, which is likely to cause problems.
Although the detailed mechanism is not known, in general, a developer, in particular, an external additive, is considered to be significantly involved in cleaning. Specifically, it is considered that a developer, in particular; an external additive, intervenes between the cleaning blade and the peripheral surface of the electrophotographic photosensitive member and functions as a granular lubricant, thus enabling stable cleaning. Consequently, in the case where image formation is continuously performed at a normal image density, by sufficiently supplying the granular lubricant between the cleaning blade and the peripheral surface of the electrophotographic photosensitive member, stable cleaning performance is exhibited.
However, for example, in the case where image formation is performed at a low coverage rate, in the case where monochrome image formation is performed in a tandem electrophotographic apparatus, or in the case where image formation is performed using an electrophotographic apparatus having very high transfer efficiency, the supply of the granular lubricant tends to become insufficient. When the supply of the granular lubricant between the cleaning blade and the peripheral surface of the electrophotographic photosensitive member becomes insufficient, cleaning performance tends to be degraded. Specific examples of the degradation in cleaning performance include inadequate cleaning due to chattering and turning up of the cleaning blade and fracturing and chipping of the edge portion of the cleaning blade. Here, the term “chattering” refers to a phenomenon in which an increase in frictional resistance between the cleaning blade and the peripheral surface of the electrophotographic photosensitive member causes the cleaning blade to vibrate. Furthermore, the expression “turning up of the cleaning blade” refers to a phenomenon in which the cleaning blade which abuts against the peripheral surface of the electrophotographic photosensitive member in a direction opposite to the moving direction of the peripheral surface of the electrophotographic photosensitive member is reversed so as to abut in the direction of the moving direction of the peripheral surface of the electrophotographic photosensitive member.
Furthermore, specific examples of the degradation in durability of the electrophotographic photosensitive member include an increase in the abrasion loss of the surface layer of the electrophotographic photosensitive member resulting from an increase in frictional resistance and occurrence of flaws due to local concentration of pressure.
In dealing with the problems, roughening of the peripheral surface of the electrophotographic photosensitive member is considered to be effective from the standpoint of reducing the cleaning load. However, currently, a further improvement is required for surface roughening techniques.
As the technique of roughening the peripheral surface of the electrophotographic photosensitive member, methods of grinding the peripheral surface of the electrophotographic photosensitive member using various mechanical means have been known.
PTL 1 discloses, in order to solve various problems, such as cleaning, a technique of roughening the peripheral surface of an electrophotographic photosensitive member (in which groove portions are formed, in the substantially circumferential direction, on the peripheral surface of the electrophotographic photosensitive member), using an abrasive tape (film-shaped abrasive).
Furthermore, PTL 2 discloses a technique of forming a protrusion/recess shape on the surface of an electrophotographic photosensitive member by subjecting the surface of the electrophotographic photosensitive member to a compression molding process using a stamper having protrusions and recesses on its surface. Specifically, PTL 2 discloses a technique of forming a shape in which peaks having apexes and valleys are regularly continued in a direction at an angle with respect to the axial direction of the electrophotographic photosensitive member, i.e., a shape provided with groove portions, on the surface of an electrophotographic photosensitive member. According to this method, it has been reported that releasability of toner is improved and the nip pressure of the cleaning blade can be reduced, thereby reducing abrasion of the electrophotographic photosensitive member.